Configuring a Pod Security Policy

A pod security policy (PSP) is a cluster-level resource that controls sensitive security aspects of the pod specification. The PodSecurityPolicy object in Kubernetes defines a group of conditions that a pod must comply with to be accepted by the system, as well as the default values of related fields.

By default, the PSP access control component is enabled for clusters of v1.17.17 and a global default PSP named psp-global is created. You can modify the default policy (but not delete it). You can also create a PSP and bind it to the RBAC configuration.

Note

• In addition to the global default PSP, the system configures independent PSPs for system components in namespace kube-system. Modifying the psp-global configuration does not affect pod creation in namespace kube-system.

• PodSecurityPolicy was deprecated in Kubernetes v1.21, and removed from Kubernetes in v1.25. You can use pod security admission as a substitute for PodSecurityPolicy. For details, see Configuring Pod Security Admission.

Modifying the Global Default PSP

Before modifying the global default PSP, ensure that a CCE cluster has been created and connected by using kubectl.

1. Run the following command:

   kubectl edit psp psp-global

2. Modify the required parameters, as shown in Table 1.

   Table 1 PSP configuration

   Item	Description
   privileged	Starts the privileged container.
   hostPID hostIPC	Uses the host namespace.
   hostNetwork hostPorts	Uses the host network and port.
   volumes	Specifies the type of the mounted volume that can be used.
   allowedHostPaths	Specifies the host path to which a hostPath volume can be mounted. The pathPrefix field specifies the host path prefix group to which a hostPath volume can be mounted.
   allowedFlexVolumes	Specifies the FlexVolume driver that can be used.
   fsGroup	Configures the supplemental group ID used by the mounted volume in the pod.
   readOnlyRootFilesystem	Pods can only be started using a read-only root file system.
   runAsUser runAsGroup supplementalGroups	Specifies the user ID, primary group ID, and supplemental group ID for starting containers in a pod.
   allowPrivilegeEscalation defaultAllowPrivilegeEscalation	Specifies whether allowPrivilegeEscalation can be set to true in a pod. This configuration controls the use of Setuid and whether programs can use additional privileged system calls.
   defaultAddCapabilities requiredDropCapabilities allowedCapabilities	Controls the Linux capabilities used in pods.
   seLinux	Controls the configuration of seLinux used in pods.
   allowedProcMountTypes	Controls the ProcMountTypes that can be used by pods.
   annotations	Configures AppArmor or Seccomp used by containers in a pod.
   forbiddenSysctls allowedUnsafeSysctls	Controls the configuration of Sysctl used by containers in a pod.

Example of Enabling Unsafe Sysctls in Pod Security Policy

You can configure allowed-unsafe-sysctls for a node pool. For CCE clusters of v1.17.17 and later versions, add configurations in allowedUnsafeSysctls of the pod security policy to make the configuration take effect. For details, see Table 1.

In addition to modifying the global pod security policy, you can add new pod security policies. For example, enable the net.core.somaxconn unsafe sysctls. The following is an example of adding a pod security policy:

apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  annotations:
    seccomp.security.alpha.kubernetes.io/allowedProfileNames: '*'
  name: sysctl-psp
spec:
  allowedUnsafeSysctls:
  - net.core.somaxconn
  allowPrivilegeEscalation: true
  allowedCapabilities:
  - '*'
  fsGroup:
    rule: RunAsAny
  hostIPC: true
  hostNetwork: true
  hostPID: true
  hostPorts:
  - max: 65535
    min: 0
  privileged: true
  runAsGroup:
    rule: RunAsAny
  runAsUser:
    rule: RunAsAny
  seLinux:
    rule: RunAsAny
  supplementalGroups:
    rule: RunAsAny
  volumes:
  - '*'
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: sysctl-psp
rules:
  - apiGroups:
      - "*"
    resources:
      - podsecuritypolicies
    resourceNames:
      - sysctl-psp
    verbs:
      - use

---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: sysctl-psp
roleRef:
  kind: ClusterRole
  name: sysctl-psp
  apiGroup: rbac.authorization.k8s.io
subjects:
- kind: Group
  name: system:authenticated
  apiGroup: rbac.authorization.k8s.io

Restoring the Original PSP

If you have modified the default pod security policy and want to restore the original pod security policy, perform the following operations.

1. Create a policy description file named policy.yaml. policy.yaml is an example file name. You can rename it as required.

   vi policy.yaml

   The content of the description file is as follows:

   apiVersion: policy/v1beta1
   kind: PodSecurityPolicy
   metadata:
     name: psp-global
     annotations:
       seccomp.security.alpha.kubernetes.io/allowedProfileNames: '*'
   spec:
     privileged: true
     allowPrivilegeEscalation: true
     allowedCapabilities:
       - '*'
     volumes:
       - '*'
     hostNetwork: true
     hostPorts:
       - min: 0
         max: 65535
     hostIPC: true
     hostPID: true
     runAsUser:
       rule: 'RunAsAny'
     seLinux:
       rule: 'RunAsAny'
     supplementalGroups:
       rule: 'RunAsAny'
     fsGroup:
       rule: 'RunAsAny'
   
   ---
   kind: ClusterRole
   apiVersion: rbac.authorization.k8s.io/v1
   metadata:
     name: psp-global
   rules:
     - apiGroups:
         - "*"
       resources:
         - podsecuritypolicies
       resourceNames:
         - psp-global
       verbs:
         - use
   
   ---
   apiVersion: rbac.authorization.k8s.io/v1
   kind: ClusterRoleBinding
   metadata:
     name: psp-global
   roleRef:
     kind: ClusterRole
     name: psp-global
     apiGroup: rbac.authorization.k8s.io
   subjects:
   - kind: Group
     name: system:authenticated
     apiGroup: rbac.authorization.k8s.io
   

2. Run the following command:

   kubectl apply -f policy.yaml

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